Synthetic lubricating composition



A. H. MATUSZAK ETAL SYNTHETIC LUBRICATING COMPOSITION I June 2, 1959 2 Sheets-Sheet 1 Filed March 21, 1956 0m O? on ON Smzimo 9 113m oz 55 Q5 5 bEz3o B1108 29.525553 Tumawi $81 avov .LSELL aos-avs Alfred H. Matuszak Arnold J. Morway QNIJJHOS HOIHM .01 ("10"!) Inventors y Attorney June 2, 1959 A'. H. MATUSZAK ET'AL SYNTHETIC LUBRICATING COMPOSITION 2 Sheets-Sheet 2 Filed March 21, 1956 2 v 8 on 2 on on 9 55E um 33 v mrm 5528 282 5 m 33 531% H MQDQI on. ow on 00 m Oh i n w ow m cm m w 09 0: OS 02 03 0Q mu) QNIJJIIOS 380.438 'OVO'I O3I'lddV 1931 as "FIVE-i 173Hs Alfred H. Mafuszak I Arnold J. Morway Inventor? Y Z} M Attorney United States Patent SYNTHETIC LUBRICATING COMPOSITION Alfred H. Matuszak, Westfield, and Arnold J. Morway, Clark, NJL, assignors to Esso Research and Engineers ing Company, a corporation of Delaware Application March 21, 1956, Serial No. 572,953

6 Claims. (Cl. 252--49.6)

This invention relates to new and improved synthetic lubricating compositions having outstanding extreme pressure-resisting characteristics. Particularly, the invention relates to extreme pressure lubricating compositions which comprise blends of dialkyl esters of dicarboxylic acids, complex esters, and critical amounts of two polymerized alkyl silicones of different molecular weights.

To meet the exacting requirements of lubricating oils having utility for the lubrication of moving metal parts which are subjected to extremely high pressures and temperatures, it has been found necessary by the industry to develop lubricants with special properties. Generally, mineral lubricating oils, even when containing large amounts of the various known additive materials, have been found to be unsuccessful for the lubrication of turbo-jet and turbo-prop aviation engines. Generally, the prior art mineral lubricating oils have failed in this lubricating service because of lack of stability at high temperatures, lack of suflicient load-carrying properties or too great a change of viscosity with temperature.

This invention is concerned with synthetic lubricating oils having characteristics which make them eminently suitable for this use. The lubricating compositions described in detail below have been found to have good temperature-viscosity relationships and extreme pressureresisting characteristics along with other desirable properties which enable them to meet stringent military specifications for this use. As was set out above, these new and improved synthetic lubricating compositions comprise blends of a dialkyl ester of a, dicarboxylic acid, a complex ester formed from three ingredients: a branched chain alcohol, a dicarboxylic acid and a glycol, and critical amounts of two different polymerized alkyl silicones. As will be pointed out in detail below, the components of the compositions must be present within certain critical limitations.

The major component of the compositions of this invention is a dialkyl ester of a dicarboxylic acid. These esters conform to the following general formula:

Rooc cr1, ,.cooR

In the formula R is a branched chain alkyl group containing from 6 to carbon atoms. This alkyl group may be derived from secondary and/ or primary alcohols such as isohexyl, secondary hexyl, 2-ethylbutyl, isoheptyl, secondary heptyl, isooctyl, capryl, 2-ethylhexyl, isononyl, isodecyl, and the like. To obtain a higher degree of thermal stability at high temperatures the esters of primary alcohols are preferred over the esters derived from secondary alcohols. Among the operable branched chain alcohols, the well known Oxo" alcohols and the aldol condensation alcohols (2-ethylhexyl, 2-ethylbutyl) are preferred. The isooctyl alcohol obtained by the carbonylation of a C olefin in the presence of a cobalt catalyst at elevated temperatures and pressures are especially preferred when adipic acid and/ or azelaic acids are involved whereas 2-ethylhexyl alcohol is preferred wher sebacic acid is employed.

The dicarboxylic acid which is esterified with the de sired alcohol to prepare the diester may be selected from the group consisting of succinic, glutaric, adipic, pimelic, suberic, azelaic, and sebacic acids, with azelaic and sebacic acids being especially preferred. The formula given above covers the operable acids when n is from 2 to 8'.

A complex ester component of the lubricating oil compositions of this invention is prepared by the interaction of a branched chain alcohol having from 6 to 10 carbon atoms (e.g., 2-ethyl hexanol, C oxoalcohol), a dicarboxylic acid having from 4 to 10 carbon atoms (e.g. sebacic acid, adipic acid), and a glycol having from- 4 to 12 carbon atoms (e.g., tetraethylene glycol). These complex esters conform to the following general formula:

ROOC (CH COO C H O OC (CH COOR In the formula above, R represents the alkyl groups of the branched chain alcohols and will contain from 6 to 10 carbon atoms. x is a number from 2 to 8 and z, is a number from 2 to 6.

The preparation of the complex ester involves methods known to the art and forms no part of the inventive concept. Briefly stated, these complex esters may be prepared in a one-step process by reacting the required molar proportions of the alcohol (2 moles), the glycol 1 mole), and the dicarboxylic acid (2 moles) together in the presence of a water entrainer and an esterification catalyst at temperatures of about 350 to 425 F., until the theoretical quantity of water is evolved. If desired, a two-step process may be employed. Two moles of a half; ester of the dicarboxylic acid and the alcohol may first be formed, followed by complete esterification of the halfester with 1 mole of the glycol; or two moles of the dicarboxylic acid are reacted with one mole of the glycol to form a glycol dicarboxylic acid ester which is then completely esterified with the alcohol. Each method gives essentially the same product equivalent in all qual: ity aspects.

' The combination of the diester component and the complex ester component of the synthetic lubricating composition comprises the lubricating oil base. The pro portions of the components may vary between relatively restricted ranges. For example, it has been found that from to 99% by volume of the diester may be blended with from 1 to 20% by volume of the complex ester. More preferred, however, are blends containing from 92 to 97% by volume of the diester with from 3% to 8% by volume of the complex ester. Especially pre ferred and contemplated in the preferred embodiment of this invention is a composition containing about 96% by volume of the diester with 4% by volume of the complex ester.

To this base composition, there is added a minor amount of an antioxidant such as purified phenothiazine, phenyl-a-naphthylamine, n-butyryl p-amino phenol, 2,6- di-tert butyl-p-cresol, etc. The proportions used may vary between about 0.25 and 2 weight percent of the antioxidant. However, satisfactory oxidation resistance for most applications will be obtained by the use of abou 1.0 weight percent of phenothiazine.

The extreme pressure characteristics of the base composition referred to above have been found to be adequate to meet most lubricating requirements for present day turbo-jet engine applications. However, it has been found that the exceptionally severe conditions inherent in lubricating present and future type turbo-prop reduction gear assemblies (heavily loaded), and advanced design turbo-jet engines for supersonic aircrafts make it necessary to enhance the extreme pressure-resisting properties of this normally acceptable lubricant without increasing the overall viscosity and corrosivity of the lubricant. This has been accomplished by the instant inven- Patented June 2, 1959 tors by the inclusion in the base lubricant of specific amounts of a polymerized alkyl silicone of a specific molecular weight range. It should be emphasized that has been done without adversely affecting the noncorrosivity of the base, a feat most difiicult to accomplish with any other load carrying agent.

A This polymerized alkyl silicone is a polymer of dimethyl silicone and has the formula:

This dimethyl silicone polymer is commercially available in several viscosity grades which represent batches of different molecular weights. It has been found that only the molecular Weight polymers corresponding to from 3 to 20 centistokes viscosity at 25 C. are applicable to the formation of the improved synthetic lubricating compositions of this invention. As will be set out in detail below, when a polysilicone having a molecular weight above the 20 cs. viscosity range is used, there is an interaction or incompatibility between the silicone polymer and the diester and the complex esters which results in undesirable insolubility of the polymer. When a polysilicone of a molecular weight range below the 3 cs. viscosity grade is used, incompatibility is not a factor but the flash point of the resulting composition is lowered considerably. Furthermore, because of this high volatility (i.e. low flash point), excessive loss of the silicone ingredient could be expected. during service should lower molecular weight or lower viscosity grade silicones be used. The loss experienced would of course depend also upon the concentration of silicone employed and upon the operating conditions to which the silicone blend is subjected. The dimethyl silicone polymer is utilized in the formulation of the compositions of this invention in amounts varying between about 2 to about 25% by weight, with from about to about by weight being especially preferred to obtain the maximum load carrying ability. Because of the unusually high load carrying ability imparted to the blend by the dimethyl silicone, it has been found that 3 to 5% silicone will generally provide suffic ient load carrying ability for most turbo applications. Furthermorethis range is reasonably economical.

When the dimethyl silicone polymers are blended with the base composition defined above, it has been found that contrary to the teaching of the prior art, the foaming characteristics of the composition are undesirably afiected. Blends containing the dimethyl silicone polymer actually foam more than blends that do not contain this polymer. It has lthUS been found necessary to include in the finished lubricating composition minor amounts of a second polymer of dimethyl silicone of a molecular weight range corresponding to about 10,000 cs or above at C., with 60,000 to 200,000 cs. being especially preferred. Ordinarily, about 0.001 to 0.005 weight percent of this high molecular weight silicone has been found to eliminate the foam-forming tendency of th e low molecular Weight silicone. In certain instances, however, concentrations of about 0.05 to 0.1 weight percent have been required to impart desirable low-foaming characteristics to the finished lubricant blend.

The preferred lubricating compositions of this invention therefore comprise the following:

Dimethyl silicone polymer (10000-200000 'CS./25 C.) (1001-01 Tricresyl phosphate 0-3 .4 EXAMPLES By admixing the components set out in detail below and heating with stirring to a temperature of about to F., lubricating compositions of the following ingredients were prepared:

{Ingredients parts by weight] Blend 1 Blend 2 donipleii ester 11: 2-ethylhei'rariol sebacic acid-tctraethylcnc glycolsebacic acid-Lethylhxanol. Complex ester B: C Oxo alcohol-adipic acid-tctraethylenc glycoladlpic acid0s Oxo alcohol.

These formulations are compared with current military specifications in Table I below:

Table I MIL-L- 780813 and MIL-L- 25330 (USAF) require- 1 2 3 ments Blends Vlscoslty at 210 F., cs Viscosity at 100 F., cs. Viscosity at 65 F., cs Pour point, F Flash point, F Panel coking at 600 F., mg Panel coking at 700 F., mg.-- Panel coking at 750 F., mg H rubber swell, percent "Foam Test:

Sequence 1...

Sequence 2 Sequence Copper corrosion, 50 hrs. at

450 F., mg

Silver corrosion, 50 hrs. at 450 s- SOD lead corrosion, 1 hr. at 8 325 F. Mg. I 13-864 neut. no..,mg. KOH/gm- 0. 10 0. 22 0. 21 Oxidation corrosion stability,

72-hrs. at 347 F., mg.-/cm.:

3:04.. 0.01 0. 01 0. 04 .2 0.00 0.02 0.01 ten 0. 01 0. 01 0. 02

Aluminum 0. 04 0. 01 0.02

Si1ver' 0. 01 0. 01 0.01 visctsity at 100 13.89 13.17 13.1

tes Viscosity, percent change 5 to +15... 3 3 3.2 3.1 Ncunnumbertncrease- 2.0 1 2 0. 90 0. 56 Low temperature sta Viscosity, cs, initial (35 13,000 max 8, 040 8, 315 12, 460

mins. Viscosity, cs. final (3 hrs. 13,000 max. 8, 256 8, 315 12, 475

37 ruins).

Viscosity, percentchange" 6.0 max..- 2. 7 0.0 0.1 Evaporation loss, percent at; 50 max 22.1 26.1 36.6 Ryder gear load, lbs./in., for 1,700 min! 3,760 3, 300 2,800

MILL 7808B. Ryder gear load, lbs./ln., for 2,800 mink. 3,760 3, 300 2,800 I MIL-b25336 (USAF).

clan-son test'load, lbs

1 MIL-11480813 Specification covers turbo-jet engine oils; MI L-Ir-25336 (USAFXSpeclficatlon.covers turbo-prop engine lubricants which are MIL-11 780813 type oils having increased load carrying ability.

SAE-SOD Testis not an MIL-L-780SB Specification requirement. A lubricant giving a .value of about 550 lbs. in this test will give about 1700 lbs/1n. in the RydcrGear Test. The test is performed in the SAE Lubricant Tester. The lubricant is run-in for two minutes at 50 lbs. load, then the load is manually increased 50 lbs. every 10 seconds until scufiing occurs. The load at which scuffing occurs is recorded and denotes the load carrying ability of the lubricant.

- Because of the viscosity requirement of 13,000 cs. maximum at -65 F. in MIL-L-7808 and MIL-L-25336 Specification, the amount of the more viscous complex esters that can be incorporated in the lubricants of this invention without exceeding this requirement will be limited. The actual amount employed will, of course, depend upon the viscosity level desired as well as the viscosities of the diester and complex ester components. The viscosities of the more desirable diesters range from 2.7 to 3.5 cs. at 210 F. and 5,000 to 10,000 cs. at 65 F. The viscosities of the complex esters are about 7 to 11 cs. at 210 F., and 100,000 to 500,000 cs. (extrapolated) at 65 F. The efiect on these viscosities of hibitor such as purified phenothiazine in the base oil blend of the compositions of this invention is necessary to prevent oxidative degradation during the life of the lubricant. The stabilizing effect of phenothiazine on the diester component is readily seen in the following examples. Its effect on the diester-complex ester bases of this invention is similar. It will be noted that with phenothiazine present, metal corrosion, solidification and acidity are held to a satisfactory level. Oxygen adsorption varying the proportions of diester-complex ester base 10 is also nil.

Di-Z-ethylhexyl sebacate C oxo adipate Percent phenothiazine- 0.0 1.0 0.0 1.0

Corrosion/oxidation stability (250 F.) weight change, mgJcmJ,

and color:

Copper 0.0 ma enta 0.06 purple.. 7.3 copper. 0.04 purple Steel- 0.01 grey 00 purple 0.01 0. Aluminum alloy- 0.01 none d Magnesium alloy 0.0l 0. Cadmium plated Steel 1.48 0 Oil evaporated, percent 5.6. 0.88.. 1. Viscosity change at 100 F., pcrcentp... 87.5.. 0.16 0. Neut. number increase, mg. KOH/ m 75 0.02.. 80 0. oxitdgtgnlratwml. Oz absorbed in 4 successive 15 minute penods 250+,, 0,0, 0, 0 250+, 0, 0, 0,0

composition may be shown by the following series of blends.

Viscosity, cs. at F. Blend A. 100% dl-isooctyl azelate 3. 35 8,475

B. 95% dl-isooctyl azelate+% complex sebacate A O. 90% di-isooctyl azelate+% complex sebacate A D. 85% di-isooctyl aze1ate+15% complex sebacate A E. 80% di-isooctyl azelate+% complex sebacate A (10.3 cs.) 4. 16, 350 F. 100% Cs 0x0 adipate 2. 79 6,460 G. 95% Cg oxo adipate+5% complex adipate B (7 cs.) 2. 90 780 H. 90% 05 0x0 adipate+l0% complex adipate B (7 cs.) 2. 99 7,005 I. 85% 0 0x0 adipate+15% complex adipate B (7 cs.) 3. 15 7, 750 J. 80% G3 oxo adipate+20% complex adipate B (7 cs.) 3. 27 9, 460 K. 70% 05 0x0 adipate+30% complex adipate B (7 cs). 3. 58 13, 300 L. 100% di-isooctyl azelate 3. 8, 475

M. 95% di-isooctyl azelate+5% complex adipate B 'N. 90% di-isooctyl azelate+10% complex adipate B 0. 85% di-isooctyl azelate+15% complex adipate B P. 80% dl-isooctyl azelate+20% complex adipate B It will be noted that about 20% i-5% complex ester will generally bring the viscosity of the base blend to the desired level of about 12,00012,500 cs. at 65 F. Because of the thickening effect of still other components or additives, the amount of complex esters incorporated will generally be less than about 10%. It is to be mentioned that the complex ester itself will carry considerably more load than any of the conventional diesters.

.As shown below, this -is reflected in the base blend which has a slightly better load carrying ability than the diester alone. It is therefore advantageous to incorporate the maximum amount of complex ester providing a satisfactory low temperature viscosity can be maintained.

It is apparent from the above data that a blend from which the oxidation inhibitor is eliminated will show very poor oxidation-corrosion resistance. Although the above oxidation/corrosion tests were carried out at 250 F 0 the current test requirement calls for 347 F. At this temperature the oxidative degradation of the inhibited materials is essentially the same as above. The uninhibited materials, however, readily degrade to solid masses. As is stated above, the low molecular weight dimethyl silicone polymer is operable in the concept of this invention only within restricted molecular weight ranges. This molecular weight range corresponds to a viscosity in centistokes at 25 C. of between about 3 and about 20. The data set out below show that as the molecular weight increases above about the 20 cs. level, the silicone polymer becomes more and more insoluble in the base blend and hazy solutions result. It is also to be seen that when the molecular Weight of the silicone polymer decreases to below about the 3 cs. viscosity level, the flash point of the resulting composition is seriously lowered. The extent of the flash point lowering will of course depend largely upon the concentration of silicone employed. Because of the high volatility of the low molecular weight silicones, high concentrations will effect greater flash point lowen'ngs. This is illustrated below with a 5 cs. silicone.

1 diisooctyl azelate+15% adipate complex ester B.

Load carrying ability of ester blends; parts by weight Base blend 100 0 Diester (vol. percent) 02, a, as,

Theinclusion of a minor amount of an oxidation in- The effect of silicone viscosity at silicone concentration of 4% on flash point and on low temperature ap-. pearance of the blend is also shown below:

is believed that in bulk the silicone molecules assume a helical configuration which possess little adhesion to metal bearing surfaces while in solution such as in the base composition of this invention the silicone molecules uncoil,

Tabl B I e 5 in which state the silicone possesses considerably greater energy of adhesion resulting in a closely packed oriented Blend Flash Appearance at film on the metal bearing surfaces. Data showing the excellent lubricating properties of the base composition con- 75 taining low concentrations of silicone polymers are given 10 in the table below. It will be seen from an examinagg g i $82 tion of Table D that as the silicone polymer content of 2csIsiuconeIII: 40o 1:110: the blend is increased, the load-carrying qualities of the 3221 20383311311: iii; 1:31:33: sngithoud. cmPositiqn Teach a i POM and t rapidly 10 cs. si1icone 430 do Do. crease until substantially no improvement is shown. This 20 435 Cloud? ex reme-pressure resist ru characteristic is shown in both so 'l' 460 P t 1. s 't' e cs 51mm iioii. Qepa epma the well known SAE-SOD test loading procedure and the Base+4% 100 cs. Silic0ne 465 Incompatible Incompatible. Sh ll 4-13 11 E P t t, This data is also graphically presented in Figures I and II of the accompanying drawing. It will be seen both from Table D below and the drawings Formulations containing the base Compositions of this that optimum extreme pressure resistance is obtained by invention and the low molecular weight silicone polymer fi contammg from abfmi 0 abOut 20 Wt. percent exhibit surprising and unexpected foaming tendencies. of 6 low molecular Welght slilfione Polymer In thls This effect is contrary to the teaching of the prior art range apparently the dimethyl silicone molecules possess which disclose silicone polymers as anti-foamants. To maxlmum energy of adhesion correct this undesirable foaming, a very small amount (0.0001 to 0.01, preferably 0.001 to .005 wt. percent) Table D of a high molecular weight dimethyl silicone polymer 10 000 to 1 000 000 preferably 0 000 to 200 000 CS LOAD GARRY ING ABILITY VS. SILICONE CONTENT OF at 25 C.) added to the blend. Data set out below show ESTER BLENDS the corrective action of this additive.

- sAE- oD Shell 4-bal1 test load, EP test 1lbs to I1110 sec.)iii caring H. S011 Table C scufi load, kg.

V I MIL- r7808 foam test 100% base (for blend 1, page 9) 475 5 5 99% base+l% dimethyl silicone (l0 cs.) 700 45 98% based-2% dimethyl silicone (l0 cs.) 750 70 75 F. sequence 200 F. sequence 75 F. sequence 97% base--3% dimethyl silicone (10 es.) 950 80 1 team volume, 2 icam volume, 3 foam volume, 96% base-4% dimethyl silicone (10 cs.) 1, 025 p 96 cc. cc. cc. 95% ease-5% dimethyl silicone (10 cs.) 1, 050 108,114

90% base-40% dimethyl silicone (10 cs.) 1, 450 85% base+l5% dimethyl silicone (10 cs.) 2,000 Blow- Final Blow- Final Blow- Final 80% base-20% dimethyl silicone (10 cs.) 1, 950 136, 150

ing ing ing 75% basal-25% dimethyl silicone (10 cs.) 1, 600

50% has -50% dimethyl silicone (10 cs.) 600 78 0% base+100% dimethyl silicone (10 cs.). 100 2;; MlL-L780S 100 0 25 0 100 0 Base (similar to blend 2 base) 235 0 40 0 260 0 Base+0.001% DC- 99 60,000 It will be understood that other additives such as rust silicone 200 0 35 0 210 0 Basel-0.002% DO- inhibitors, detergents, V.I. nnprovers, auxiliary load carryggt i gtggm es. 130 0 2O 0 m 0 ing agents, etc. can be added to the present compositions. miq fil" It has also been found and forms another object of ggg g g 30 0 15 0 30 0 this invention that the synthetic lubricating compositions i fjbf as set out in detail above may be utilized in the preparaggg ggg 20 0 10 0 20 0 tion of high pressure lubricating grease compositions. s eetene These lubricating greases are prepared by thickening the "ggg g g 0S 15 0 m o 15 0 synthetic lubricants above to a grease consistency with a Base+0.oi 7;'5 55 grease-forming soap.

Zgggggg m 0 1O 0 15 0 More particularly, the present lubricating grease com- Base+ecds 7lfii positions comprise (1) about 15 to 30% by weight of a 99 grease thickener and (2) about 70 to by weight of a silicone 20 0 15 0 20 0 Based-0.005% Doblend of (a) about 10 to 20% by weight of dimethyl 99 200,000 50 silicone polymer having a viscosity at 25 C. of about 3 silicone 20 0 10 0 20 0 Basel-0.005% Doto 20 centistokes and (b) about 80 to by weight of a igg gq gi dialkyl ester of a dicarboxylic acid having the formula: insoluble) 30 0 20 0 50 0 Base+0.005% DG- RO0C(CH ),,COOR

200 1,000,000 cs. .1 silicone (some- 0 what incompawherein R represents a branched chain alkyl group, contlble) 0 15 0 5D 0 taining 6 to 10 carbon atoms and n is an integer from 2 to 8. A particularly preferred dialkyl ester is diisooctyl azelate. The soap thickener may be a grease-forming The effect of the low molecular Weight silicone poly- 70 me 1 a grease-form"? mfif/tal Soap-Salt complex mar on the load-carrying ability of the base composiof a metal soap of a carboxylic acid and metal salt of a tion of this invention is most unusual since the base comcarboxyli a l Prefefffid metals are the alkaline earth position and especially the silicone separately are by com- 019E315, and Preferred molar P P of Salt to P are parison poor lubricants. The exact mechanism by which 1n the range of about 3. 5 :1 to 20: 1. The soap thickeners this phenomenon occurs is not clearly understood, but it 75 utilized 111 the formulation of the grease compositions of 9 this aspect of the invention and the calcium soap of commercial caprylic acid.

Samples of the grease compositions of this invention are set out in detail below:

Preparation-The same procedure was used in both samples A and B. The dry preformed lithium soap was slurried in the ester or ester-blend and heated to 410 F. while stirring. The other ingredients (inhibitors) were then added and the molten grease was poured in shallow layers in pans for quick cooling. (Other rapid cooling means may be employedv as long as the grease remains quiescent during passage through transition point.) The cold grease was returned to kettle, stirred to required penetration and milled or homogenized, filtered and packaged.

Non- Silicone Properties silicone containing blend A blend B Appearance Excellent Excellent Dropping point, F 360 360 Penetrations, 77 F. min/10:

Unworked 285 285 Worked, 60 strokes-.- 295 295 Worked, 100,000 stroke 342 342 Low temp. performance, 65 F., time to 811121 a 204 bearing under 2,000 gram-cm. lna Load carrying performance in Shell 4-ball E.P. test- Scar diameter at given load, mm.-

32 kg 0.36 0. 26 40 kg i 0.50 0.28 50 kg 0. 75 0.30 63 kg 1.00 0. 32 79 kg. 1. 79 0.37 100 kg 2.00 2 0. 38 126 kg Weld Weld Average 3 balls measured in 2 directions 1 Less than 5 secs. Up to and including this load there was no sent! or film rupture.

18% lauric, 58% caprlc, 24% ceprylic (Sap. No. 324).

Preparation-The lime and ester or ester-silicone blend was charged to a fire heated kettle and heated to 135 F. A blend of acetic and caprylic acids was then added and heating continued to 500 F. The heat was then shut oil and the mass cooled to 200 P. where phenyl alpha naphthylamine was added and the grease further cooled to 15 0 F. At that temperature the grease was homogenized and packaged.

are preferably lithium stearate or a complex formed from the calcium salt of acetic acid N on-Slli- Silicone Properties cone Blend Containing O Blend D Appearance Excellent Excellent Dropping point, F 500+ 500+ Penetrations, 77 F. m

Unworked 276 275 Worked, 60 strokes 280 280 Worked, 100,000 strokes 325 325 Extreme pressure properties:

Shell 4-ba1l test scar diameters at given load 0. 26 0. 28 0. 29 0. 30 0. 31 0. 30 0. 38 0. 33 0. 47 0.37 0.72 0. 40 0.90 0. 44 1. 25 0. 49 1. 30 0. 95 2. 20 1. 10 316 kg Weld 2. 50 E.P. value (calculated) (based on Hertz loadings) 52. 5 86.5

1 Up to this point inclusive there was no apparent scuff or film rupture.

What is claimed is:

1. A fluid synthetic lubricating composition having improved extreme pressure resisting characteristics consisting essentially of (l) a major proportion of a lubricating oil base consisting of (a) 80 to 99% by volume of a dialkyl ester of a dicarboxylic acid having the formula:

ROOC(CH ),,CO0R wherein R represents a branched chain alkyl group containing 6 to 10 carbon atoms and n is an integer from 2 to 8 and (b) 1 to 20% by volume of a complex ester having the formula:

ROOC(CH COO (C H O) OC(CH COOR wherein R represents a branched chain alkyl group containing 6 to 10 carbon atoms, x is an integer from 2 to 8 and z is an integer from 2 to 6; (2) about 0.25 to 2% by Weight, based on the lubricating oil base, of an antioxidant; (3) about 2 to 25% by weight, based on the lubricating oil base of dimethyl silicone polymer having a viscosity at 25 C. of about 3 to 20 centistokes; and (4) about 0.001 to 0.1% by weight, based on the lubricating oil base, of a second dimethyl silicone polymer having a viscosity of 25 C. of at least about 10,000 centistokes.

2. A fluid synthetic lubricating composition having improved extreme pressure resisting characteristics consisting essentially of (1) a major proportion of a lubricating oil base consisting of (a) 92 to 97% by volume of a dialkyl ester of a dicarboxylic acid having the formula:

ROOC(CH ),,COOR

wherein R represents a branched chain alkyl group containing 6 to 10 carbon atoms and n is an integer from 2 to 8 and (b) 3 to 8% by volume of a complex ester having the formula:

ROOC (CH COO C H O OC(CH COOR wherein R represents a branched chain alkyl group containing 6 to 10 carbon atoms, x is an integer from 2 to 8 and z is an integer from 2 to 6; (2) about 0.25 to 2% by weight, based on the lubricating oil base, of phenothiazine; (3) about 3 to 5% by Weight, based on the lubricating oil base, of dimethyl silicone polymer having a viscosity at 25 C. of about 3 to 20 centistokes; and (4) about 0.001 to 0.005% by weight, based on the lubricating oil base, of a second dimethyl silicone polymer having a viscosity at 25 C. of about 60,000 to 200,000 centistokes.

3. A fluid synthetic lubricating composition having improved extreme pressure resisting characteristics consisting essentially of (1) a major proportion of a lubri- 11 cating oil base consisting of (a) 92 to 97% by volume a: a" dialkyl ester of a dicarboxylic acid having the to m a i ROOC(CH COOR wherein R represents a branched chain alkyl group containing 6 to 10 carbon atoms and n is an integer from 2 to 8 and (b) 3 to 8% by volume of a complex ester having the formula:

ROOC(CH COO(C H O) OC(CH ,COOR

wherein R represents a branched chain alkyl group containing 6 to 10 carbon atoms, x is an integer from 2 to 8 and z is an integer from 2 to 6; (2), about 0.25 to 2% by Weight, based on the lubricating oil base, of phenothiazine; (3) about 5 to 20% by weight, based on the lubricating oil base, of dimethyl silicone polymer having a viscosity at 25 C. of about 3 to 20 centistokes; and (4) about 0,001 to 0.005% by weight, based on the lubricating oil base, of a second dimethyl silicone polymer having a viscosity at 25 C. of about 60,000 to 200,000 centistokes.

4. A fluid synthetic lubricating composition having improved extreme pressure resisting characteristics consisting essentially of (1) a major proportion of a lubricating oil base consisting of (a) about 95% by volume of diisooctyl azelate and (b) about 5% of a complex ester of 1 mol of tetraethylene glycol with 2 mols of sebacic acid and 2 mols of Z-ethyl hexanol; (2) about 1% by weight, based on the lubricating oil base, of phenothiazine; (3) about 5% by Weight, based on the lubricating oil base, of dimethyl silicone polymer having a viscosity at 25 C. of about 10 centistokes; and (4) about 0.001% by weight, based on the lubricating oil base, of dimethyl silicone polymer having a viscosity at 25 C. of about 60,000 centistokes.

5. A fluid synthetic lubricating composition having improved extreme pressure resisting characteristics consisting essentially of (1) a major proportion of a lubricating oil base consisting of (a) 97% by volume of 2-ethyl hexyi sebacate and (b) about 3%v by volume of complex ester of 1 mol of tetraethylene glycol with 2v mols of adipic acid and 2 mols of C branched chain primary alcohol; (2) about 1% by weight, based on the. lubricating oil base, of phenothiazine; (3) 4% by weight, based on the lubricating oil base, of dimethyl silicone polymer having a viscosity at 25 C. of about 10 centi: stokes; (4) about 0.001% by Weight, based on the lubricating oil base, of dimethyl silicone polymer having a viscosity at 25 C of about 60,000 centistokes; and (5) about 1% by weight, based on the lubricating oil base, of tricresyl phosphate.

6. A fluid synthetic lubricating composition having improved extreme pressure resisting characteristics consistlng essentially of (l) a major proportion of a lubricating oil base consisting of (a) about 38% by volume of C branched chain primary adipate, (b) about 57% by v.01-v ume of C branched chain primary adipate and (c) about 5% by volume of a complex ester of 1 mol tetraethylene glycol with 2 mols of adipic acid and 2 mols of C branched chain primary alcohol; 2) about 1% by Weight, based on the lubricating oil base, of phenothiazine; (3) about 5% by Weight, based on the lubricating oil base, of dimethyl silicone polymer having a viscosity at 25 C. of about 10 centistokes; and (4) about 0.001% by weight, based on the lubricating oil base, of dimethyl silicone polymer having a viscosity at 25 C. of about 60,000 centistokes.

References Cited in the file of this patent UNITED STATES PATENTS 2,407,037 Sowa Sept. 3, 1946 2,589,317 Young et al. Mar. 18, 1952 2,750,341 Morway et al. June 12, 1 956 

1. A FLUID SYNTHETIC LIBRICATING COMPOSITION HAVING IMPROVED EXTREME PRESSURE RESISTING CHARACTERISTICS CONSISTING ESSENTIALLY OF (1) A MAJOR PROPORTION OF A LUBRICATING OIL BASE CONSISTING OF (A) 80 TO 99% BY VOLUME OF A DIALKYL ESTER OF A DICARBOXYLIC ACID HAVING THE FORMULA: 